The present invention relates to a copier, printer, facsimile apparatus or similar image forming apparatus and more particularly to a measure against a jam in a fixing device included in an image forming apparatus.
Generally, an image forming apparatus includes a fixing device for fixing a toner image transferred to a paper sheet or similar recording medium by heating the toner image. To detect a jam likely to occur in the fixing device, a paper sensor may be positioned downstream of a heat roller, which is included in the fixing unit, in a direction in which the paper sheet is conveyed. When the paper sensor senses the leading edge of the paper sheet, it is determined that the paper sheet did not jam the fixing unit.
However, when a separator disposed in the fixing device for peeling off a paper sheet catches the paper sheet, the paper sensor does not sense the leading edge of the paper sheet. Further, the operator of the apparatus cannot easily see the inside of the fixing device, which is enclosed in a casing for heat insulation, or find a paper sheet left therein. The apparatus is therefore likely to resume its operation with a paper sheet remaining in the fixing device, causing a jam to be repeated.
Technologies relating to the present invention are disclosed in, e.g., Japanese Patent Laid-Open Publication No. 6-122257.
It is therefore an object of the present invention to provide an image forming apparatus capable of obviating a jam ascribable to a paper sheet left in a fixing device, but not sensed by a paper sensor.
It is another object of the present invention to provide an image forming apparatus facilitating even the removal of a paper sheet jamming a path extending over a fixing unit and a unit adjoining it.
In accordance with the present invention, an image forming apparatus capable of dealing with a recording medium jamming a fixing device includes a body to which the fixing device is removably mounted. The fixing device is pulled out of the body in the event of a jam occurred therein to thereby allow the jam to be removed. A fixing device sensor senses the fixing device when the fixing device is mounted to the body. A medium sensor is disposed in the fixing device for sensing a recording medium. When a jam occurs in the fixing device without the medium sensor sensing a recording medium, the apparatus is prevented from resuming its operation unless the set condition of the fixing device on the body being sensed by the fixing device sensor is interrupted.